Low-Temperature Adsorption of Carbon Monoxide on Gold Surfaces: IR Spectroscopy Uncovers Different Adsorption States on Pristine and Rough Au(111)

Abstract

The morphology of gold surfaces plays a major role in many domains of contemporary research. Infrared (IR) spectroscopy in combination with carbon monoxide (CO) as a probe adsorbate is able to sensitively monitor differences in the morphology of gold surfaces on an atomic level if CO adsorption on the various surfaces is clarified.Our investigation comprises the first study of CO adsorption on Au(111) under welldefined ultra-high vacuum conditions at 30 K. We find that CO adsorbs on Au(111) in atop geometry as has been reported before for a variety of gold surfaces but a significantly higher frequency of the internal CO stretching vibration is observed confirming results from recent theoretical studies. Furthermore, the presence of a submonolayer amount of gold adatoms on the Au(111) surface results in the properties of gold surfaces towards CO adsorption at higher temperatures known from literature.Step-wise annealing of these atomically rough surfaces leads to a gradual transition between the literature case and the behavior observed on the pristine Au(111) surface at 30 K.

Elucidation of Active Sites for the Reaction of Ethanol on TiO2/Au(111)

“…27,29 After annealing the sputtered Au(111) surface to 400 K, the desorption feature at Tdes=172 K increases in intensity, while the desorption feature for undercoordinated Au sites (Tdes=185 K) decreases, indicating that the 400 K anneal results in a smoother Au(111) surface. While sputtering the surface results in an increased number of undercoordinated sites of both step edges and kink sites, 23,[25][26][27][28] the peak at 185 K is assigned to Au step edges, as the concentration of step edges is expected to be much greater than that of kink sites. The adsorption energies of ethanol on Au(111) terrace sites and Au step edges can be calculated using the Redhead approximation for first-order desorption where  is the heating rate of 1.05 ± 0.07 K/s and  is the pre-exponential factor.…”

Enhancing the reactivity of gold: Nanostructured Au(111) adsorbs CO

“…While CO does not adsorb on the Au (111) and (110) surfaces at low pressures and temperatures, its adsorption was reported for the (322) surface [15], (211) stepped single crystal surfaces [16] and for the (111) surfaces structurally modified by ion sputtering [3,17]. Recent work carried out under UHV conditions at very low temperature (30 K) demonstrated CO adsorption on the pristine and on the gold adatoms modified Au(111) surfaces [18].…”

Vibrational Relaxation Lifetime of a Physisorbed Molecule at a Metal Surface

“…In addition, the fit to the SFG spectrum yields an amplitude ratio for CO to Au contribution: a 01 =jχ ð2Þ Au j ¼ 0.19 AE 0.02 and the phase φ 01 ¼ 14°AE 4.0°. The SFG spectrum also shows enhanced intensity between 2100 and 2115 cm −1 , indicating CO molecules adsorbed at defect sites of the surface [37].…”

“…2(a) and 2(b), respectively. The vibrational resonances at 2131 cm −1 are both assigned to the internal stretch fundamental of CO adsorbed on Au(111) terraces [37]. A small additional absorption between 2100 and 2115 cm −1 [Fig.…”

“…A small additional absorption between 2100 and 2115 cm −1 [Fig. 2(a)] arises from CO molecules bound at undercoordinated adsorption sites [35,[37][38][39], which represent ∼1% of the surface area on our sample. The SFG spectrum exhibits a differential line shape arising from interference between the CO vibrational resonance and Au SFG 532 nm plasmon resonance.…”